Methods for producing instant noodles can be broadly divided into methods for producing fried (deep-fried) noodles and methods for producing non-fried noodles. Fried noodles are produced by frying gelatinized noodle strings in oil at about 150° C. and then drying the fried noodle strings. On the other hand, non-fried noodles are produced by drying gelatinized noodle strings by a drying method other than deep frying. There are some drying methods, but a general drying method is a hot-air drying method in which noodle strings are dried by blowing hot air having a temperature of about 70 to 100° C. and a wind speed of about 5 m/s or less onto the noodle strings for about 30 minutes to 90 minutes. Other drying methods are a low-temperature drying method in which noodle strings are dried for a long period of time at low temperature and a high-temperature and high-speed air drying method in which high-temperature and high-speed airflow having a temperature of about 100° C. to 200° C. is blown onto noodle strings (see, for example, Patent Literature 1).
Noodle strings of non-fried noodles produced by hot-air drying have a firmer inside structure than those of fried noodles, and therefore the non-fried noodles have a texture closer to that of fresh noodles. Fried noodles are easily loosened at the time of cooking and eating. This is because when noodle strings are fried in oil, their shape is fixed while the noodle strings float to the surface of the oil due to moisture evaporation, and therefore a noodle block is relatively bulky and sticking together of the noodle strings is also relatively less likely to occur. On the other hand, hot air-dried non-fried noodles are produced by putting gelatinized noodle strings into a retainer and drying the gelatinized noodle strings with air, and therefore the noodle strings are gravitationally compressed downward and are likely to come into contact with each other. Particularly, at the bottom of a noodle block, the noodle strings are closely packed together and are therefore likely to stick together, which results in poor loosening at the time of cooking and eating. Further, at the time of cooking, hot water is hard to penetrate into a part where the noodle strings stick together, which causes a problem that such a part is not rehydrated with hot water and therefore has an unpleasant texture.
Meanwhile, conventional instant noodles are generally noodles called “wavy noodles” produced by subjecting noodle strings cut out with a cutting blade to waving treatment in a box-shaped duct called “wave box” placed directly below the cutting blade. In this case, it is possible to reduce contact points between the noodle strings overlapping one another, which is advantageous in that the noodle strings are less likely to stick together also in the step of gelatinization.
On the other hand, reflecting diversified consumer tastes, instant noodles using noodles called “straight noodles” have recently become popular, whose noodle strings have no wave or are less wavy and therefore become substantially straight when rehydrated with hot water (see, for example, Patent Literatures 2 and 3). When such straight noodles are produced by gelatinizing noodle strings by steaming or the like, putting the gelatinized noodle strings into a retainer, and drying the gelatinized noodle strings with hot air, the noodle strings are more likely to be closely packed together as compared to wavy noodles. Particularly, the noodle strings near the bottom surface of the retainer tend to be remarkably dense due to the weight of the noodle strings located thereon, and are therefore more likely to stick together during drying as compared to non-fried wavy noodles. Further, it takes much time to dry the noodle strings due to poor circulation of hot air, which leads to another problem of uneven drying. This also causes poor loosening and rehydration at the time of eating, uneven rehydration, uneven texture, breakage during storage or the like.
As a conventional method for improving the loosening of non-fried noodles, a method is known in which a loosening agent is added to noodle strings by mixing the loosening agent in the noodle strings or by attaching the loosening agent to the surface of the noodle strings (see, for example, Patent Literatures 4 and 5). When such a conventional method is used, loosening-improving effect can be obtained to some degree, but cannot be sufficiently obtained because it is impossible to avoid noodle strings from being closely packed together due to their own weight so that the noodle strings stick together during drying.
Further, as a technique for preventing the sticking of noodle strings, a method is known in which an emulsion is attached to noodle strings in the middle of steaming or just after steaming, and compressed air is blown onto the noodle strings to loosen the noodle strings (see, for example, Patent Literature 6). This method can prevent the sticking of noodle strings during steaming, but cannot sufficiently obtain loosening-improving effect because the moisture content of the noodle strings is not reduced before drying, and therefore the noodle strings are closely packed together due to their own weight and stick together during drying.
Further, as a technique for improving the loosening of noodle strings by reducing the density of the noodle strings to provide gaps between the noodle strings, a method is known in which the moisture content of noodle strings before drying is reduced (see, for example, Patent Literature 7) or a noodle block is dried to be bulky (see, for example, Patent Literature 8).
The method described in Patent Literature 7 is one in which a liquid seasoning containing emulsified animal and vegetable oil and fat is attached to gelatinized noodle strings, the gelatinized noodle strings are heated with overheated steam so as not to be puffed, and the heated noodle strings are dried. According to this method, noodle strings are heated with overheated steam having high energy before the noodle strings are cut, which causes the noodle strings to stick together. Therefore, there is a problem that the noodle strings cannot be well stretched or are broken in the step of stretching noodle strings before cutting so that the noodle strings after cutting vary in weight. On the other hand, since the moisture content of the noodle strings is reduced before drying, the noodle strings can be prevented from being closely packed together due to their own weight. However, the noodles are hard to loosen at the time of eating because of the occurrence of sticking before drying. As a result, noodles that are easily loosened cannot be obtained.
The method described in Patent Literature 8 is one in which hot compressed air is blown from below noodle strings after the noodle strings are dried to a predetermined moisture content. This method is not sufficiently effective, either, because the density of the noodle strings increases due to their own weight before hot compressed air is blown, and therefore the surface of the noodle strings is slowly dried and becomes increasingly viscous, which reduces the loosening effect of hot compressed air.